Key Engineering Materials Vols. 529-530

Abstract: Calcium phosphates films were deposited onto pipes and stents of nitinol alloys by an electrolytic deposition (ELD) method. Monocalcium phosphate (Ca (H₂PO₄)₂·H₂O) solutions were used as the electrolyte, and electric depositions were carried out at the constant cathode current of 1.59 mA/cm² at 65°C for 60 min. From the deposition on nitinol pipes, deposition rates were changed in 15 minutes and the precipitates were identified to be octacalcium phosphate (Ca₈H₂(PO₄)₆·5H₂O) and dicalcium phosphate anhydrous (CaHPO₄). The electrolytic depositions on the nitinol alloys were useful for the formation of calcium phosphates films on the complex shape of stents.

Abstract: To improve surface hardness of dental implant made of pure titanium (Ti), titanium nitride (TiN) coating was introduced. However, studies revealed that TiN only showed osseointegration similar or inferior to that of Ti. Therefore it is necessary to improve the biocompatibility of TiN for dental implant coating. In the present study, TiN coating was prepared on pure Ti substrates and hydrothermal treatment was conducted to modify its surface properties. It was found that, TiN surface was partially oxidized after treatment and calcium (Ca) was successfully combined onto its surface. Surface morphology, roughness and hardness were not affected after treatments below 140°C and wettability was obviously improved.

Abstract: Zinclipscombite (ZnFe³⁺₂(PO₄)₂(OH)₂) coating layer was prepared on 316L SS. The 316L SS plates were treated using hydrothermal treatment at 200°C for 2, 6 and 24 h. The ZnFe³⁺₂(PO₄)₂(OH)₂ layer strongly attached to the 316L SS surface. The adhesive strength of the coating layer was measured higher than 65.7 ± 3 MPa. The surface observation and element analysis indicated that the 316L SS plates were covered with ZnFe³⁺₂(PO₄)₂(OH)₂ coating layer after hydrothermal treatment. Linear voltammograms for treated sample at 200°C for 24 h showed higher corrosion resistance. The ICP results proved protective property for the zinclipscombite coating agains PBS solution.

Abstract: Nacreous coatings on orthopedic implants can be advantageous because of its robust mechanical properties, high biocompatibility, and ability to promote bone growth. The biofabrication of nacreous coatings on conventional orthopedic implant materials via biomineralization process from abalone shells was examined. The objective was to investigate the effect of different materials on nacreous coating growth. The coatings were characterized by SEM/EDS and XRD. It was found that different materials resulted in different surface morphologies and coating thicknesses, although the main mineral formed was aragonite. Calcium carbonate coating was formed on the entire surface of the poly (methyl methacrylate) and high density polyethylene implants and resulted in a thick coating, while the titanium implants showed thinner coating at the same growing period.

Abstract: The objective of the study was to compare clinical efficiency of the fusion after reconstruction with an anatomically shaped PEEK cage associated with a iliac crest autograft or MBCP in the treatment of cervical disc disease in randomized clinical trial. A multicente randomized, comparative and prospective study on 58 patients, with a 12 months follow up are reported. They underwent anterior cervical decompression and fusion being randomized for autologous graft or MBCP. Patients presenting purely degenerative disc disease were implanted with a PEEK cage filled with iliac crest autograft or MBCP. Pain and functionality as well as patients satisfaction were assessed through VAS, Neck Disability Index (NDI) and Patient Satisfaction index were recorded until 24 month follow-up. Radiological evaluation included plain and dynamic short X-rays at each stage of the follow up. The patients satisfaction rates was of 82% in the autograft group versus 96% in the MBCP group. Pain at the donor site was significantly more important in the autograft group at 3 weeks, 3 months and 1 year follow-up. No implant failures were recorded. Previously goat preclinical study was performed. Micro CT, light microscopy and shistomorphometry were related to the high performance of the MBCP insert for filling cage fusion, completing the clinical assessment of our clinical study. The use of MBCP insert is safe and avoids potential graft site morbidity and pain in comparison with an autologous graft procedure.

Abstract: A new composition of bioactive glass was proposed that can be drawn into fibers, woven into cloth, and has appropriate alkali-releasing ability for bioactivity. The glass was drawn into fibers and woven into cloth, then the biological efficacy of the cloth was examined in in vivo tests. Bone defects made in tibial bones of Wistar rats were covered with the cloth just like "bandage" for two weeks. The cloth was found to promote new bone formation in the bone defects without causing any adverse effects. In contrast, excessive infection was recognized and new bone was not formed when cloth made of E-glass fibers was used. This was the first successful demonstration that glass cloth made of bioactive glass fibers assisted bone regeneration. The present glass cloth, therefore, is expected to be a promising material for "bone bandage" or porous scaffolds for bone tissue regeneration.

Abstract: Most of edentulous areas need reconstructive procedures of hard tissues for an ideal implant position. In this perspective, guided bone regeneration with semi-permeable membranes or onlay bone grafts harvested from intra-or extra-oral sites is indicated. Establishment of well regulated tissue banks allows surgeons use of allograft bone. This study compares two clinical cases, where a relevant horizontal deficit was present: first one reconstructed with allograft bone + titanium mesh and the other one with onlay graft + autogenous cortico-spongiosa bone particles, harvested from ramus. In both cases plasma rich in growth factors and fibrin membranes were used in order to enhance graft vascularization and osseous regeneration, as well as faster healing.

Abstract: We recently synthesized a novel unidirectional porous hydroxyapatite (UDPHAp) material with a microstructure consisting of cross-sectional oval pores (diameter, 100-300 μm) . The unidirectional pores of UDPHAp are expected to facilitate the ingrowth of new tissues at sites of implantation. Here, we estimated the osteoinductive capacity of UDPHAp following its implantation in the dorsal muscles of dogs, and also investigated the affinity of UDPHAp for muscle and connective tissues. As a reference material, the HAp porous ceramic product Apaceram^® (HOYA, Tokyo, Japan), which is commercially available in Japan and has a different microstructure from UDPHAp, was also used. A cylinder-shaped UDPHAp block was implanted in the dorsal muscles of two beagle dogs. At 1 and 2 years post-implantation, muscle and connective tissues had directly attached to UDPHAp at the upper and lower perforated surfaces. Histological assessment, revealed the direct invasion of fibrous tissues and small capillaries into the unidirectional pores of UDPHAp. Notably, no osseous tissue had formed within UDPHAp. Our findings suggest that the unidirectional pores of UDPHAp are advantageous for the vascularization and invasion of fibrous tissues. However, this unique structure does not contribute to osteoinductive capacity.

Abstract: The purpose of this study was to examine the effects of ceramic femoral head material on the wear of annealed, crosslinked ultra-high molecular weight polyethylene (UHMWPE) (XLPE) in total hip arthroplasty compared to non-crosslinked conventional UHMWPE (CPE). XLPE was fabricated by crosslinking with 60 kGy irradiation and annealing. Femoral heads made from zirconia and alumina ceramics, and cobalt-chrome (CoCr) of 22 mm or 26 mm diameter were used. In this study, the femoral head penetration into the cup was measured digitally on radiographs of 70 hips with XLPE and 50 hips with CPE. The average follow-up periods were 6.1 and 12.7 years, respectively. The steady wear rate of XLPE was significantly lower than those of CPE (0.002 versus 0.08 mm/year, respectively). Zirconia displayed increased wear rates compared to alumina in CPE; however, there was no difference among head materials in XLPE (0.0028, 0.011 and 0.009 mm/year for zirconia, alumina and CoCr, respectively). Neither head size or implantation period impacted XLPE wear. In contrast to CPE, XLPE displayed low wear rates surpassing the effects of varying femoral head material, size, implantation period and patient demographics.

Abstract: The aim of the described study was to generate and evaluate a putty-like bone graft substitute ready to use for dental and orthopedic surgery. According to the asking of clinicians the new material should avoid the necessity of mixing blood and bone graft during the surgical process. Therefor the granulous material NanoBone^® has been combined with a hydrogel based on Polyvinylpyrrolidone (PVP) and tested in standardized rat tibia defect over a period of 12 weeks and evaluated histologically. The results showed no limitations of the granulate characteristics in matrix change and hence a high level of vascularization and bone formation. An example for dental application shows the outcome in the case of socket preservation.